President Barack Obama and first lady Michelle Obama are scheduled to join tens of thousands of local mourners, dozens of other foreign leaders at the memorial service Tuesday for former South African President Nelson Mandela, the Associated Press reports.

South African officials told the AP that the crowd would likely surpass the normal seating capacity of Johannesburg's FNB stadium, where security is expected to be tight, as the list of presidents, heads of government, royalty and celebrities continues to grow.

Beside the Obamas, the AP reports, the list includes former presidents George W. Bush, Bill Clinton and Jimmy Carter; U.N. Secretary General Ban Ki-moon and his predecessor Kofi Annan; British Prime Minister David Cameron and French President Francois Hollande.